What Causes Tomato Plants to Be Purple?

Tomatoes are a common home garden crop.

Tomatoes are an easy-to-grow plant for many home gardeners. With proper care and maintenance, tomatoes provide plenty of fresh, juicy fruit. However, if you notice purpling of your tomato leaves or leaf veins, this could signal a small problem, such as temperature fluctuations, or a more serious problem, such as psyllid infestation. Detecting these problems early is the best way to protect your tomato plants.

Temperature

Tomato plants prefer warm weather and should not be planted outdoors until the temperature remains at a steady 50 degrees Fahrenheit. Planting tomatoes outdoors too early or in a greenhouse that is too cool can cause the leaves of young plants to turn purple. Even if the daytime temperatures are warm in spring, the nights may be too cool for tomatoes and this change in temperature can cause the leaves to curl and turn purple. This is generally a short-term problem, but it can slow the tomato plant's growth.

Phosphorus Deficiency

Tomatoes suffering from phosphorus deficiency exhibit symptoms such leaves showing purple veins or with an overall purple color. Other symptoms include a bronze coloring of leaves and a red color along vein margins. Managing this problem requires adding phosphorus to the soil. This is done by adding bone meal to the soil or using Epsom salt (the magnesium helps soak up the phosphorus) as a foliar spray.

Curly Top Virus

Curly top virus symptoms vary by host plant; affected tomatoes show symptoms including curling leaves, veins turning purple on the underside of leaves and a light green discoloration. Other symptoms include stunted growth and distorted leaves. The beet leafhopper transmits curly top virus. There are no effective chemical controls, so the best form of management and prevention is to use row covers on tomato plants to keep leafhoppers away.

Psyllid Infestation

Psyllids are small insects that can do extensive damage to tomatoes and other crops. These pests inject their toxic saliva into plant leaves and can kill young tomato plants.The leaves of affected plants turn yellow and the veins turn purple, a condition known as psyllid yellows. Because these pests are so tiny, damage usually occurs before they are detected. Check tomatoes for signs of infestation, so you can treat plants right away using a broad spectrum insecticide, beneficial insects or organic pest products.

About the Author

Based in Indiana, Molly Allman holds a B.A. in professional writing. She works as both a writer and author and enjoys writing articles on many different topics. She specializes in topics concerning health, crafts, family and lifestyles. Her fiction writing appears in "Bewildering Stories," "The Other Herald" and "Spectacular Speculations."